JPS6316564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to gas turbine engines, and more specifically, to apparatus for minimizing rotor-to-shroud clearance during both steady state and transient operation.

As turbine engines become more reliable and efficient through changes in methods, design, and materials, losses caused by excessive clearance between relatively rotating parts are becoming more widespread. It has become increasingly important from a design point of view.
Many turbine engine applications require operating at variable steady state speeds and switching between these speeds as desired during normal operation. For example, jet engines of the type used to power aircraft require the pilot to be able to shift to a desired speed at a time of his choosing. Due to the resulting changes in temperature and rotor speed, relative elongation between the rotor and the surrounding shroud must be accommodated. The main concern is how to prevent frictional interference between the rotator and the rotor, as this will cause friction and increase the radial clearance during subsequent operation. However, the gap between them should be kept to a minimum. Given the transient operating conditions previously described, the pattern of relative mechanical and thermal expansion between the rotor and shroud creates a very difficult problem.

In order to reduce the clearance between the rotor and the shroud, various schemes have been devised to vary the position of the stationary shroud in response to engine operating parameters. This one method was published in the U.S. patent.
This is a thermally operated valve as described in No. 3966354. In this device, the valve operates in response to the temperature of the cooling air, taking into account transient conditions to the extent that the temperature of the cooling air is related to the speed of the engine. However, this device has a relatively slow response and tends to be relatively inaccurate in trying to match relative growth during transient operations.

Perhaps the main reason why cooled air systems operating solely on a speed response plan are inadequate is that such systems cannot handle the heat during rotor heating and cooling for all possible operating sequences during transients. This is probably because the time constant cannot be taken into account. That is,
Current equipment can only match the rotor thermal time constants when the transient operating sequence is known. Of course, this is not sufficient, since the particular mode of operation and sequence of operations will depend on the conditions at the time.

Briefly, in one aspect of the invention, a timing valve is responsive to a rotor speed signal to schedule temperature changes to air flow relative to a shroud support of a turbine to match a thermal time constant of the rotor. I'll do it like that. This minimizes the clearance between the rotor and the shroud during both transient and steady state operation.

In another aspect of the invention, the timing valve is actuated when a predetermined level of rotor speed is reached. The valve then advances at a constant speed, planning an incremental increase in the temperature of the air.

Another aspect of the invention is to vary the air temperature by using two air sources with different temperatures.
These sources are selectively used, either independently or in combination, to provide four different airflow conditions.

In yet another aspect of the invention, the timing valve begins to retract at a constant rate toward its initial position when the rotor has decreased to a predetermined speed level.
The backward speed is slower than the forward speed to avoid any interference between the rotor and the shroud. During the retraction phase, air delivery is determined by rotor speed and is independent of timing valve position.

Another aspect of the invention is that the timing valve continues to advance for a predetermined period of time after reaching the highest temperature airflow condition, and thus during the retraction period, the extra time gained allows it to rotate. The rotor is sufficiently cooled so that the speed of the rotor can rapidly increase without friction.

Another object of the invention is that the scheduled action of the timing valve is predetermined by operating the rotor at a predetermined speed. The temperature of the delivered air is then determined only by the rotor speed and is independent of the timing valve position.

FIG. 1 shows a portion of a typical gas turbine engine. The gas turbine engine includes a row of circumferentially spaced high pressure turbine blades 11 surrounded in close proximity by a plurality of circumferentially spaced shroud sections 12. In normal operation of a single-stage high-pressure turbine, hot exhaust gas from a combustion device (not shown) passes through a row of high-pressure nozzles 13, a row of turbine blades 11, imparting rotational motion to the blades, and Further, it flows to one row of low pressure nozzles 14 on the downstream side. As is well known, cooling air is supplied from the high pressure cooling chambers 16 and 17 to the high pressure nozzle 13 and the low pressure nozzle 14.

The shroud portion 12 has a shroud support structure 18
Supported by. This support structure has inner flanges 19, 21 which are interconnected with the shroud portion by an annular clamping bracket 22 and a support bracket 23. To cool the shroud section 12, cooling air from the cavity 24 is passed through the support bracket 23 into the cavity 26, where it is passed through holes in the shroud plate 27.
It is customary to provide cooling to the shroud section 12.

A shroud support ring 18 is supported at its forward end by attachment to the combustion device casing 28 and at its rear end by attachment to the nozzle support element 29 and the low pressure turbine casing 31, and is supported by attachment to the intermediate flange. 32 and a rear flange 35. These flanges have considerable thickness and radial height;
It accounts for a significant portion of the total mass of the shroud support structure 18. By selectively controlling the temperature of these flanges and therefore their thermal elongation,
Shroud support structure 18 and shroud portion 1
2 is modulated to follow the mechanical and thermal elongation of the rotating vane 11 to minimize the clearance between the vane 11 and the shroud portion 12 during steady-state and transient operation. It will be understood that it is possible to suppress the

A manifold 33 surrounds the shroud support structure. The manifold 33 is connected at its front end to the combustion device casing 28 by a plurality of coupling members 34, and at its rear end by a plurality of coupling members 36.
It is connected to the turbine casing 31. The manifold 33 forms the outside of a high-pressure cooling air high-pressure chamber 37 and a low-pressure cooling air high-pressure chamber 38 , and the two high-pressure chambers 37 and 38 are separated by a wall 39 . The walls 39 can be provided with means for creating a slight air flow between the hyperbaric chambers, as indicated by the arrows. that is, from high pressure cooling air high pressure chamber 37 or by passing the air across the top of flange 19 after it has hit flange 19, and/or by providing a separate supply conduit 41 as shown, low pressure cooling air high pressure chamber 38. It is possible to supply cooling air to Cooling of the low pressure nozzle takes place in a known manner.

A bleed air conduit 42 communicates with the high pressure cooling air high pressure chamber 37 . The bleed air conduit receives bleed air at varying temperatures from the compressor, as will be described in more detail below. The radially inner boundary of the cooling air high-pressure chamber as well as the radially outer boundary of the inner high-pressure chamber 43 are constituted by impingement rings 44 .
This ring has a plurality of holes 4 spaced apart in the circumferential direction.
6 is provided to blow relatively high pressure air from the high pressure chamber 37 onto the surfaces of the intermediate flange 32 and the rear flange 35 to control their temperature. After this, the impinged air normally exits the high pressure chamber 43 at a relatively intermediate pressure, cooling other elements of the engine.

High pressure cooling air high pressure chamber 37 via bleed air conduit 42
The flow of cooling air directed to is planned by the apparatus generally shown in FIG. In this figure, the main fuel control unit 47 receives an input representative of rotor speed.
generates a plurality of fluid pressure outputs that are used to operate a timer 48 and a pair of pneumatic valve actuators 49, 51 having pneumatic valves 55, 60, respectively, to operate manifold 52 and thus conduit 42. Plan the air to be routed through the shroud support.

Within the main fuel control system 47 are a pair of pressure-balanced fluid pressure signal valves 53, 54 (see FIG. 3) each having a plunger 56, 57, the position of each plunger being valve stem 59,
61 is controlled by a cam 58 that engages 61. Cam 58 is positioned in response to a core speed tachometer commonly used to schedule fuel flow for acceleration as well as compressor stator position. This two-valve system has a specific speed hysteresis band at each switch point to prevent the system from switching back and forth between modes when operating near the switch point speed. The shape of the cam is such that once the switching point displacement is achieved, the captured plunger is moved by the differential pressure to the opposite extreme of its stroke within the range of the valve stem stop. It is designed to drive the valve stem inside each valve. Therefore, the velocity must change by an amount corresponding to the stroke of the plunger before the signal returns to the original gap of the valve. Since the stroke of the plunger is limited to a range corresponding to the speed hysteresis band, this has a negligible effect on the shroud clearance.

Each signal valve 53, 54 receives three hydraulic inputs, which are readily available from conventional existing fuel control systems. The inputs are P _B (boost pressure), P _CR (P _B +100 _psi ) and P _C (P _B +200 _psi ). Each plunger 56, 57 is energized by a cam 58 such that a combination of these pressures is obtained at the respective signal valve such that the output turbine clearance signals TC ₂ and TC ₁ are equal to P _B or P _C . positioned. Two fluid pressure signals TC ₁ and TC ₂ are sent along with fluid pressure signal P _B to a timer 48 which generates fluid pressure signals on lines 62 and 63 which actuate pneumatic valve actuators 51 and 49, respectively. These valve actuators receive a pressure input signal to use as a reference pressure.
You will also receive a _PCR . An actuator responds to the fluid pressure signal from the timer 48 to actuate the air valves 60, 55 to provide different amounts of stage 5 and stage 9 cooling air for use in controlling the temperature of the shroud support. The combination is delivered to the air valve discharge port or manifold 52.

Referring to FIG. 4, timer device 48 is shown to include a dual diameter cylinder 64 and a dual diameter piston 66. A helical spring 71 is disposed within the large end 67 of the cylinder between one wall 68 thereof and the large end 69 of the piston, which directs the piston towards the head side at the left end of the cylinder 64. blank space 70
There is a tendency to be biased towards. Three axially spaced lands 7 on the smaller end 72 of the piston
3, 74, 76, and these lands extend radially outwards to form the smaller end 7 of the cylinder.
It forms a close gap with the inner wall of 7. A passage 78 extends axially through the piston 66 from one end to the other, and an orifice 80 at one end meters the flow of fluid into the head cavity 70. Piston port 79 connects passage 78 to lands 74,7
6 is in fluid connection with a cavity 81 located between 6 and 6. There is also a passage 82 in the smaller end 72 of the piston, which fluidly connects the cavity 83 between the lands 73, 74 with the larger end 67 of the cylinder.

Hydraulic connections to the cylinder 64 are made by lines 84, 86, 87 at the small end and by line 88 at the large end. Piping 84 enters the end of the smaller portion 77 of the cylinder and connects to the signal valve 53 provided in the main fuel control device 47.
Convey pressure fluid with pressure TC ₂ coming from. Piping 86
is connected to the side of the smaller portion 77 of the cylinder, and the other end is connected to one end of the highest pressure selector 89. One end of the piping 87 is connected to the smaller end 77 of the cylinder, and the other end is connected to the maximum pressure selector 91
connected to one end of the One end of the pipe 88 is connected to the wall 68 of the large end 67 of the cylinder, and the other end is connected to the mixing valve 92. The mixing valve 92 is comprised of a cylinder 93 in which a double-sided piston 94 is disposed, and a helical spring 96 that biases the piston 94 to a lower position as shown. The upper end of cylinder 93 is fluidly connected by piping 97 to signal valve 53 of main fuel control device 47, to which fluid pressure TC ₂
Add. The lower end of the mixing valve 92 is connected by a fluid line 98 to the other signal valve 54 of the main fuel control device 47 and receives the fluid pressure signal TC ₁ . Fluid piping 8
8 is connected to the larger end 67 of the cylinder, but enters the mixing valve 92 at the midpoint between the two ends, and the pressure
Another fluid line 99 carrying fluid P _B also enters the cylinder 93 at approximately the same axial point. Finally, fluid piping 101 extends from a point at the lower end of cylinder 93 to the other end of maximum pressure selector 89. The operation of the mixing valve 92 in various conditions will be explained later.

Next, the maximum pressure selectors or selection valves 89, 91 will be described. Each has a ball 102, 103, the position of which is determined by the pressure acting on it, and only the maximum pressure experienced by the ball is determined by the respective ball 102, 103. Air can flow to valve actuators 51 and 59. For example, maximum pressure selection valve 8
At 9, the ball 102 is subjected to pressure in the lines 86, 101 and moves such that only the higher pressure enters the line 62 and into one end of the pneumatic valve actuator 51.
Similarly, valve 91 operates so that only the higher pressure from line 87 and line 98 enters line 63 and into one end of pneumatic valve actuator 49.

As shown in FIG. 4, the air valve 55 is normally closed.
The actuator 49 is biased by a helical spring 104 with a pressure fluid at pressure P _CR . Air valve 60 is a normally open valve whose actuator 51 is biased by helical spring 106 and pressure fluid at pressure P _CR .

The operation of timer 48 in steady state idling speed conditions will now be described. At idle speed, cam 58 (see _{Figure 3} )
Plungers 56 and 57 are moved to positions where low pressure P _B exists at both signal points. At this time,
This low fluid pressure is present in piping 84, cylinder small end 77, passage 78 and head cavity 70 shown in FIG. 4, and piston large end 69.
It acts on The opposite side of the larger end of the piston 69 is connected to a pipe 9 via a pipe 88 and a mixing valve 92.
is subjected to the same low pressure P _B from 9. Since the pressures are equal, the piston 66 remains in this position.
Since the same low pressure is in line 86 and fluid enters mixing valve 92 via line 99 at pressure P _B , line 10
The pressure at No. 1 is also low pressure P _B. Therefore, the pressure in the pipe 62 is P _B , and the spring 106 and the fluid at the pressure P _CR keep the actuator 51 in the retracted state and the valve 60 in the open position, allowing stage 9 air to flow to the discharge port 52 of the valve. Make it.

At the same time, the fluid at low pressure P _B is transferred to the highest pressure selector 91
Pipes 98, 87 leading to the air valve actuating device 4
It also exists in the pipe 63 at the left end of 9. Opposite the pneumatic valve actuator 49, the force of the spring 104 as well as the fluid pressure P _CR acts, thus causing the valve 55 to
is held in a normally closed position, preventing fifth stage air from flowing to the air valve's discharge port 52.

The mixing valve 92 receives pressure fluid at a low pressure P _B at both ends thereof, so that the piston 94 remains in the downwardly biased position shown.

Operation of the device in a steady-state idle mode of operation is accomplished by using relatively hot stage 9 air to quickly set the shroud position and provide the necessary clearance for operation. However, this will be explained in more detail later. In addition to the idle mode of operation, the device is designed to operate over the entire core speed range and, for convenience of explanation, includes steady state modes of operation, i.e., cruise, climb, etc., as shown in the table in Figure 5. and in the case of takeoff,
The case of a standard day is shown. It will be appreciated that this steady state mode of operation uses progressively hotter air as engine speed and temperature increase to match the thermal expansion of the rotor. That is, after the initial start-up and idling operation, the coldest air source from stage 5 is used in the cruising range of 10,000 to 13,400 rpm, and then the fifth and ninth stages are mixed in the climb range of 13,400 to 14,000 rpm. ,lastly
For steady state takeoff operating regimes higher than 14000rpm,
Only air is used in the ninth stage to ensure proper clearance during takeoff operations on hot days.

Looking at the table in FIG.
If the engine remains in the reverse position as shown in the figure, or if the engine is running at a higher speed and drops to one of these speed ranges, as will become clear later on,
It will be appreciated that the timer piston 66 is retracted and moved to the left toward the position shown in FIG.
In the other two modes of operation, climb and takeoff,
The timer piston 66 advances to schedule progressively higher air temperatures as shown.

FIG. 6 graphically depicts the various control signals, final piston position, air source used and rotor to shroud clearance for each steady state mode of operation. During the idle mode, both TC ₁ and TC ₂ are low pressure signals P _B so the piston is in the leftmost position. Stage 9 uses only air, and the rotor-to-shroud clearance is the highest possible at this speed. As the speed increases to the cruise range, the control signal TC ₁ increases to the P _C level, turning off the 9th stage air and turning on the 5th stage air. This results in a substantial reduction in the rotor-to-shroud clearance, which continues to decrease as the speed increases into the ascending range. When the speed increases to the above range, the signal TC ₂
increases to the P _C level and the piston of the sequence timer moves to the rightmost final position. At this time, turn on the 9th stage air, mix the 5th stage and 9th stage air,
Increase the rotor to shroud clearance to the acceptable level shown. When the speed increases to the take-off level, this clearance decreases and the signal TC ₁ drops to the P _B level, cutting the fifth stage air and increasing the rotor-to-shroud clearance, even if the speed increases further. , to prevent friction from occurring as a result.

Reference is now made to FIG. 7 to explain the operation of the device during transient conditions. FIG. 7 graphically depicts the timer valve piston position as well as the air valve position for an engine operating from idle to takeoff and then back to cruise/idle. Following this sequence, the control parameters and the position of the valve with respect to time will be considered with reference to FIGS. 8A to 8M.

As shown in FIG. 4, when the engine is in the idle position, stage 9 air is delivered to the shroud support to provide adequate clearance between the rotor and the shroud. When the engine is accelerated to takeoff range, the system begins to operate as shown in Figure 8A, and over time,
The actions shown in FIGS. 8B, 8C, and 8D are performed sequentially.

In FIG. 8A, fluid pressure signal TC ₁ is at a low level P _B and signal TC ₂ is at a high level P _C . Therefore, the high pressure fluid in the piping 84 passes through the passage 78 and the orifice 80 to the head side cavity 70 on the left side of the piston 66.
and thus begin to move the piston to the right. At the same time, the high pressure fluid in line 86 lowers the ball 102 of the highest pressure selector 89, and the high pressure fluid enters line 62 and acts against the pressure P _CR in spring 106 and pneumatic valve actuator 51, causing the piston to move. It acts to extend the air and close off the 9th stage air. The rest of the circuit remains in the low voltage P _B condition.
This no-flow condition is represented by the first 30 seconds of movement. At this time, the timer valve piston has moved to the right by 20% of its stroke, as shown in FIG.

After 30 seconds, the piston has moved to the right to the position shown in Figure 8B. At this point, high pressure fluid enters port 79 and cavity 81 and then flows to line 87 where ball 103 of maximum pressure selector 91 is lowered as shown. High pressure fluid enters line 63 and overcomes the spring force and pressure P _CR to extend actuator 49 and open normally closed valve 55, thus allowing stage 5 air to enter the valve's discharge port 52. . In this state, as shown in FIG.
When 6 moves to the 30% position, it lasts for 15 seconds.

After 45 seconds, land 73 of piston 66 connects to pipe 8.
6 to the right of the port leading to port 6 and shuts off the high pressure fluid supply to this piping (see Figure 8C).
The pipe 86 is then subjected to the action of fluid at low pressure P _B entering via the pipe 88, the large end 67 of the cylinder, the passage 82 and the cavity 83. At this time, the pipe 62
The pressure drops to a low level P _B and the pressure P _CR retracts the actuator and moves the air valve 60 to the normally open position. At this time, the ninth stage air enters the discharge port 52,
The air in the 5th stage and the 9th stage is mixed, and this state is
This continues for the next 40 seconds until the piston 66 advances to the 57% position as shown in FIG.

After a total of 85 seconds (see Figure 8D), land 76 is to the right of the port leading to pipe 87 and low pressure P _B
The fluid in the pipe 88 and the large end 6 of the cylinder
7, and a low pressure state is applied to the highest pressure selector 91. Since low pressure is applied to both sides of the maximum pressure selector 91, low pressure fluid is present in the pipe 63, and the pressure P _CR
returns actuator 49 to the left, placing air valve 55 in the strip position shown and shutting off the fifth stage air supply. As shown in FIG. 7, in this state, the piston 6
It lasts for the period from 85 seconds to 150 seconds when 6 moves to the rightmost position. Continued advancement beyond the point at which the air valve 55 closes is called overshoot, and this was included in the design by extending the timer piston retraction time to allow the rotor to cool sufficiently and increase speed. This is to prevent friction from occurring even if there is a sudden increase. This will be explained in more detail later.

As long as the rotor speed remains above the 14000 rpm level, the piston remains in the rightmost position and stage 9 air continues to flow to the shroud support. As the speed decreases from a takeoff speed of 14,000 rpm to a lower speed requiring another steady state regime, such as 13,400 to 14,000 rpm, or a cruise range of 10,000 to 13,400 rpm, the system changes to provide another cooling regime. For example, when the speed drops to the 13,400-14,000 rpm range, a mixed flow of stages 5 and 9 immediately occurs. When the speed drops to the cruising range, the system is immediately adjusted to supply only stage 5 air to the manifold. At this point, the speed
Below the 13400 rpm level, the timer begins to run backwards, following the downward slope shown in FIG. The timer piston takes 150 to advance all the way to the right.
Note that it takes only seconds and 650 seconds to retreat completely to the left. The rotor takes longer to cool down at low speeds than it takes to heat up at high speeds, so in order to prevent the rotor and shroud from rubbing against each other in the event of a rapid increase to a high thrust state, , it is necessary to slow down the retreat in this way. Needless to say, overtravel of the piston over a period of 65 seconds results in approximately 280 seconds of extra retraction time. This time allows the high inertia rotor to cool sufficiently while the shroud cooling system remains in its hot mode of operation so that it does not rub against it, for example due to repeated upsurges.

When the speed drops to a level below 13400rpm,
The piston retracts to the left and the fifth stage air valve remains open as shown in Figures 8E-8H. In Figure 8E, as the speed drops below the 13400 rpm level, signals TC ₁ and TC ₂ switch, with TC ₁ becoming the high pressure _PC and TC ₂ becoming the low pressure _PB . When the higher level pressure signal TC ₁ is in the piping 98, the highest pressure selector 91 and the piping 63, the normally closed air valve 55 is opened by the _PC , and the fifth stage air is sent to the air valve discharge port 52. Allow it to flow. at the same time,
The signal of high pressure TC ₁ enters the mixing valve 92, and the piston 9
4 to the upper position, set high pressure fluid to the piping 101, the highest pressure selector 89 and the piping 62,
The normally open air valve 60 is closed to prevent stage 9 air from entering the air valve discharge port 52. The low pressure P _B signal TC ₂ passing through the passage 78 and the orifice 80 to the head cavity 70 is not large enough to overcome the force of the helical spring 71, so that the piston 66 begins to retreat to the left. do. At the end of the 280 second period,
The piston 66 is in the position shown in FIG. 8F,
Land 76 passes to the left of the port entering line 87 and low pressure from line 84 is present at port 79, cavity 81 and line 87. Maximum pressure selector 91
At this time, the ball 103 moves to the upper position as shown, and high pressure fluid still flows from the pipe 98 to the pipe 6.
3 and finally to the air valve actuator 49 to keep the air valve 55 in the open position.

After 450 seconds, piston 66 has moved to the position shown in FIG. 8G, with land 73 passing to the left of the port entering pipe 86. There is a low pressure above the ball 102 and a high pressure below the ball and the piping 62 and air valve 51 to keep the air valve 60 in the closed position.

After 650 seconds of cruising operation, the piston 66 moves to the 8th H
Land 74 has been moved to the far left position shown in the figure, and land 74 has passed to the left of the port entering piping 87, exposing this piping to low pressure P _B and allowing fluid at this pressure to pass through piping 88. It passes through a passage 82 and a void 83. At this time as well, the high pressure fluid from the pipe 98 passes through the highest pressure selector 91 and the pipe 63, and the air valve 55
The device will remain in this state as long as cruising speed is maintained.

During a period of time as the piston 66 is retracting, as shown by the downwardly sloping line in FIG.
If the cruise mode threshold of 13400rpm is exceeded,
The piston 66 begins to move forward in reverse to the right according to the advance plan previously described. However, instead of advancing the piston 66 from the leftmost position, it begins from where the retraction stopped. For example, after 200 seconds of retreat,
As the speed increases to the takeoff level of 14,000 rpm, the piston 66 travels 70% of its stroke as shown in the graph of FIG.
It has retreated to position A. Thereafter, the piston starts moving forward from the illustrated position B according to the forward plan, and at that time, only the fifth stage cooling air is changed to only the ninth stage cooling air.

the engine is running at cruising speed for 200 seconds,
When the piston 66 is in position A of FIG. 7 and the engine is then accelerated to the 13,400 to 14,000 rpm range, the system is adjusted to the condition shown in FIG. 8I.
In this view, both signals TC ₁ and TC ₂ are at high pressure P _C and high pressure fluid enters passageway 78, orifice 80 and head cavity 70, reversing the orientation of piston 66 and From point B, proceed in the opposite direction according to the forward plan. A high pressure signal TC ₁ flows along line 98, through top pressure selector 91, line 63 to air valve actuator 49 to hold valve 55 in the open position and allow stage 5 air to flow. At this time,
Mixing valve 92 has high pressure at both ends, so piston 94 remains in the spring biased lower position shown and low pressure signal P _B is applied to lines 101, 86 and maximum pressure selector 89. The pressure fluid entering the piping 62 and the pneumatic valve actuating device 51 is at low pressure;
The air valve 60 is opened to allow stage 9 air to flow to the air valve's discharge port 52. Therefore, this mixed flow regime continues while the machine is operated within the ramp speed range of 13,400 to 14,000 rpm.

Then, if the device has been operating in cruise mode for the entire 650 seconds and piston 66 has therefore moved to the leftmost position, the fifth stage air continues to flow. At this time, when the speed is increased to an increasing range of 13,400 to 14,000 rpm, the timer starts moving forward again from the zero position shown in FIG. 7 and sequentially advances through the various states shown in FIGS. 8J to 8M. In Figure 8J, both TC ₁ and TC ₂ are high voltage signals P _C . High pressure signal TC ₂ is pipe 8
4. Air valve 60 for piping 86 and piping 62
keep it in the closed position. A high pressure signal TC ₁ is passed via line 98 and line 63 to air valve actuator 49 to hold valve 55 in the open position and allow stage 5 air to enter the air valve's discharge port 52.

After 30 seconds, piston 66 has moved to the position shown in FIG. 8K, with land 74 passing to the right of the inlet to pipe 87. To this end, high pressure fluid from piping 84 enters port 79, cavity 81 and piping 87, applying high pressure fluid to both sides of ball 103. High pressure is still applied to line 63 and pneumatic valve actuator 49, keeping valve 55 in the same open position as before.

After 45 seconds, piston 66 has advanced to the position shown in FIG. 8l, with land 73 passing to the right of the port entering line 86. At this time, the pipe 88,
Low pressure P _B from passage 82, cavity 83 and piping 86
of fluid creates a low pressure condition in piping 62 and air valve 60
moves to a normally open position to allow stage 9 air to also pass to the available discharge port 52.

After 85 seconds of operation, piston 66 has moved to the position shown in FIG. 8M, with land 76 passing to the right of the port entering line 87. This applies low pressure fluid to the highest pressure selector 91, allowing the ball 103 to move to the position shown. However, high pressure fluid from line 98 still flows into line 6.
3 and pneumatic valve actuator 49 to keep valve 55 in the open position. As long as the ascending mode of operation continues, the mixing of stage 5 and stage 9 air continues, causing piston 66
starts the overshoot mode. When the speed then decreases to cruise or idle mode, the piston reenters the slope retreat plan shown in FIG.

Those skilled in the art will appreciate that various combinations of the specific cooling devices described herein may be chosen without departing from the scope of the invention. For example, although the present invention has been described with respect to operating at particular core speeds and ranges, other schemes may be used to suit any particular operating conditions.
Similar implementations are possible depending on speed and application. Additionally, this plan can be periodically modified slightly if necessary to compensate for changes in performance that have occurred over time. Other possibilities include the use of other air sources, velocity sensing devices and/or support cooling devices.

[Brief explanation of the drawing]

1 is an axial cross-sectional view of a turbine shroud support according to a preferred embodiment of the invention; FIG. 2 is a schematic diagram of a turbine shroud cooling arrangement according to a preferred embodiment of the invention; and FIG. 3 is a preferred embodiment of the invention. FIG. 4 is a partially schematic cross-sectional view of the speed sensing portion of the present invention; FIG. 4 is a partially schematic cross-sectional view of the timer and air valve of the present invention; FIG. FIG. 6 is a graph showing the relationship of various parameters during steady state operation; FIG. 7 is a graph showing various sequence valve positions and air valve positions as a function of time; FIGS. 8A-8M are graphs showing the relationship of various parameters during steady state operation; 1 is a diagram illustrating a series of positions of valves and air valves as they go through a typical driving cycle; FIG. Explanation of main symbols, 11... Rotating blade, 12... Shroud portion, 18... Shroud support structure, 37...
High pressure cooling air high pressure chamber, 42...bleeding conduit, 47...main fuel control device, 48...timer, 55, 60...air valve.

Claims (1)

[Scope of Claims] 1. Air delivery for supplying air of varying temperature to a compressor, a rotor, a shroud, a shroud support surrounding the rotor, in combination with an apparatus of the type having a shroud support surrounding the rotor. In the apparatus, the air delivery device comprises: (a) first and second air sources such that the temperature of the second air source is higher than the temperature of the first air source; and (b) the first air source. and first and second air valves respectively controlling the flow of air from a second air source to the manifold; (c) means for delivering air from the manifold to the support; and (d) the rotor. in response to the speed of the rotor and the time after reaching the predetermined rotor speed.
a timer valve that is actuated when the rotor speed reaches a predetermined level, the timer valve receiving a first predetermined rotor speed signal; a piston that advances at a first substantially constant speed when received and retracts at a second substantially constant speed when a second predetermined rotor speed signal is received, the valve means controlling the translation of the piston; Apparatus for actuating the first and second air valves in response to. 2. The air delivery device according to claim 1, wherein the first and second air sources are compressor bleed air sources. 3. The air delivery device according to claim 1, wherein the first air source is an intermediate stage of a compressor. 4. The air delivery device according to claim 1, in which the second air source is located downstream of the compressor. 5. The air delivery device according to claim 1, wherein the first air valve is a normally closed valve. 6. The air delivery device according to claim 1, wherein the second air valve is a normally open valve. 7. The air delivery device of claim 1, wherein the valve means is responsive to two fluid pressure signals representative of a predetermined speed range, and the differential pressure between the two fluid signals is substantially constant. Device. 8. The air delivery device of claim 1, wherein the piston continues to advance for a predetermined period of time after receiving a predetermined rotor speed signal. 9. The air delivery device according to claim 1, wherein the piston is biased by a spring. 10. The air delivery device according to claim 1, wherein the piston is moved at a constant speed by fluid pressure acting on one end of the piston. 11. The air delivery device according to claim 1, wherein the piston has a fluid passage extending longitudinally therethrough. 12. In the air delivery device according to claim 1, the valve means has two valves for each air valve.
A device that supplies one of two pressure inputs. 13. An air delivery device for providing airflow to the shroud support in response to rotor speed, in combination with a device of the type having a compressor, a variable speed rotor, a shroud, and a shroud support surrounding the rotor. wherein the air delivery device comprises: (a) air valve means for selectively varying the temperature of the air; and (b) means for timing operation of the rotor after it has been accelerated to a predetermined operating level. the rotor advancing at a first predetermined speed when the rotor accelerates to the predetermined operating level and retracting at a second predetermined speed when the rotor decelerates to the predetermined operating level. (c) further comprising means for actuating said air valve means in response to translation of said piston of said means (b). 14. The air delivery device of claim 13, wherein the air valve means includes first and second on/off air valves. 15. The air delivery device according to claim 13, wherein the air valve means includes a normally open valve and a normally closed valve. 16. An air delivery system according to claim 13, wherein said air valve means controls the flow of extracted air from a compressor. 17. The air delivery device of claim 14, wherein the air valve means includes two air sources having different temperatures. 18. The air delivery device according to claim 15, wherein the two air sources are composed of extracted air from an intermediate stage and a rear stage of a compressor. 19. An air delivery device according to claim 13, wherein said means (b) is activated when the rotor speed reaches a predetermined level. 20. The air delivery device of claim 13, wherein said piston continues to advance for a predetermined period of time after receiving a predetermined rotor speed signal, and said means (b) advances for a portion of said predetermined time. A device that operates only for a while. 21. An air delivery device according to claim 13, wherein the piston is advanced by fluid pressure acting on one end thereof. 22. The air delivery system of claim 13, wherein said air valve means is responsive to a pressure input thereon, and wherein said means for varying air temperature provides a reference pressure input to said valve means. 23. The air delivery system of claim 22, wherein said means for varying air temperature provides both a high pressure input and a low pressure input to said valve means.